1. Field of the Invention
The invention relates to an exposure device which is used for production of a substrate such as a printed board, a liquid crystal substrate, or the like. The invention relates particularly to an exposure device which divides a substrate into several rectangular exposure zones and gradually exposes the respective exposure zones.
2. Description of Related Art
In an apparatus for the production of a semiconductor device, a unique process is carried out where a mask pattern, which has been formed on a mask, is exposed onto a wafer substrate to be treated. In this process the following is done:
The area to be exposed on a wafer is divided into several areas;
The mask pattern is projected onto the above described areas which have been formed by the division;
A substrate carrier, on which the wafer has been placed, is moved by a given amount; and
The above described exposure areas which have been formed by division are moved in rows to an exposure position and progressively exposed.
This process is generally called step-and-repeat exposure.
Conventionally, except for the above described apparatus for production of a semiconductor device, the exposure of a workpiece in fields, for example in the field of producing a printed board, a liquid crystal substrate or the like, overall exposure has been performed in which a mask is prepared which is essentially the same size as the substrate and in which the entire exposure area of the substrate is exposed at once. Recently, however, in the above described fields the step-and-repeat exposure process is being used more often to prevent enlargement of the mask corresponding to the enlargement of the substrate.
When the mask becomes large, the disadvantages are that the production costs for the mask become greater, and that, as a result of the mask""s own weight, the exposure precision decreases, as well as similar disadvantages. In a step-and-repeat exposure process the size of the mask can be made smaller than the size of the substrate and thus the above described defects can be eliminated.
The above described exposure device for the step-and-repeat exposure process for a printed board, a liquid crystal substrate or the like is disclosed, for example, in Japanese patent disclosure document JP 8-62850 (patent 2904709: proximity exposure system) and in Japanese patent disclosure document JP 9-82615 (patent 2994991: projection exposure type, U.S. Pat. No. 5,881,165).
When a printed board, liquid crystal substrate or the like is exposed, there are many cases in which the area onto which the mask pattern is transmitted and exposed is rectangular (the lengthwise and the transverse sides being of different length). This circumstance is also dependent on what kinds of parts are being produced. When the above described exposure area has a rectangular shape, the area in which the mask pattern is produced also has a rectangular shape.
It is described in Japanese patent disclosure document JP 11-260705 and Japanese patent disclosure document JP 2000-98619 that the individual lenses which comprise the compound lens have a rectangular shape. These compound lenses (hereinafter called the integrator lens) are located in the light source part of an exposure device in order to irradiate the rectangular exposure area with high efficiency. In compound lenses several lenses are located parallel to one another in the lengthwise and transverse direction.
The above described integrator lens is an optical element which is used generally for an exposure device or the like. It is positioned to make uniform the distribution of the illuminance of the light emitted onto the surface to be exposed. The integrator lens is formed by several lenses being located parallel to one another in the lengthwise and transverse direction. The integrator lens is located at a position at which the light emitted from a lamp is focused by means of a condenser mirror or located in the vicinity of this position.
In the aforementioned documents (Japanese patent disclosure documents JP 11-260705 and 2000-98619), it is described that the individual lenses comprising the integrator lens have a rectangular shape when the shape is viewed from the direction of the optical axis in order to irradiate the rectangular irradiation area without reducing the light utilization factor.
When light from a lamp is incident on an integrator lens in which there are several hexagonal column-shaped or cylindrical lenses next to one another, the light emerging from this integrator lens has an essentially circular cross section. When this circular irradiation shape is emitted unaltered onto a mask and is cut off at a right angle by the mask pattern, the amount of unused light is increased, by which the utilization factor of the light becomes low.
If, on the other hand, an integrator lens is used in which there are several columns with a rectangular cross section next to one another, and when the cross sectional shape of the light emerging from this integrator lens according to the mask pattern is changed into a rectangular shape, the light that is wasted is reduced resulting in the light utilization factor becoming higher. This increases both the illuminance and also the throughput. When light is incident on an integrator lens with such an arrangement, the shape which the emerging light forms on the irradiation surface becomes a shape similar to the shape of the above described individual lenses, when viewed from the direction of the optical axis, even if the cross section of the incident light is circular.
FIG. 3 shows one example of an exposure device which emits rectangular light using the above described integrator lens and progressively exposes the exposure areas on a printed board. In FIG. 3, reference number 1 labels a lamp and reference number 2 labels a condenser mirror which focuses the light from the lamp 1. This focused light is incident via a reflector 3 on an integrator lens 4. The shape of the integrator lens 4 is identical to the shape described in the aforementioned documents. The integrator lens 4 is formed by several lenses being located parallel to one another in the lengthwise and transverse direction, and has a cross section, in the direction perpendicular to the optical axis, which has a rectangular shape. The light emerging from the integrator lens 4 is shaped into a rectangle, as is described in the aforementioned documents, is then reflected by a reflector 5 to be incident on a collimator 6 to be converted into parallel light and emitted onto a mask 7. A mask pattern on the mask 7 is recorded on a rectangular area to form a mask pattern. This mask pattern is projected via a projection lens 8 onto the surface of a substrate 10 to be exposed, such as a printed board or the like, which has been placed on a workpiece carrier 9. By moving the workpiece carrier 9 in the X-Y directions the substrate is progressively moved, and in the exposure area of the substrate the mask pattern is progressively exposed.
A projection exposure device is described above. But the same also applies in a proximity exposure device in which, without using a projection lens, a mask and a substrate are caused to approach one another and a mask pattern is exposed onto the substrate.
The light utilization factor is improved since the rectangular shaped light is emitted onto the mask by means of the integrator lens. However, with respect to changes in the shape of the area to be exposed on the substrate, multi-purpose applicability is lost. This aspect is described below.
It is desirable for different mask patterns to be exposed in one exposure device. The size and shape of the area on the substrate onto which a pattern is exposed is changed by the different types of products to be exposed and different processes employed.
It was described above that when a printed board, a liquid crystal substrate or the like is exposed, the area onto which the mask pattern is transmitted and exposed (hereinafter called the exposure zone) generally has a rectangular shape (the lengthwise and transverse sides being of different length). But cases arise in which production is possible with higher efficiency when the exposure zones on a substrate are more wide than long and are next to one another, as is shown in FIG. 4(a), or in which production is possible with higher efficiency when the exposure zones are located next to one another on a substrate and are more long than wide, as is shown in FIG. 4(b). Therefore, cases occur in which the exposure zones, due to different products being produced or different processes, are arranged in the manner shown in FIG. 4(a) or in the manner shown in FIG. 4(b), even if a substrate with the same shape is used for each exposure. This means that the arrangement of the respective exposure zones on the substrate is chosen such that the respective exposure zones are located most effectively on the substrate according to the differences of the products to be produced and the processes employed.
Assuming that in an exposure device an integrator lens is installed for a pattern which is more wide than long, and that the exposure zones shown in FIG. 4(a) are exposed by means of light which is more wide than long, an entire mask pattern which is more long than wide cannot be irradiated; even when using a device for exposure with light which is more long than wide and which is shown in FIG. 4(b). In one such case, either the integrator lens is replaced by an integrator lens which can irradiate with light which is more long than wide, or the substrate is turned by 90xc2x0 and placed on the workpiece carrier. Here the disadvantages are the following:
(1) It is necessary to make available two integrator lenses if the integrator lens is to be replaced. Since each integrator lens is formed by a combination of several quartz lenses which have been processed with high precision, the production costs rise. Furthermore, that integrator lens which is not being used must be stored such that neither cloudiness or scratches are formed on the lens surface. This increases the storage costs.
(2) After replacing the integrator lens, it is necessary to carry out calibration and confirmation so that the optical axis of the light incident on the integrator lens agrees with the optical axis of the integrator lens. When the two optical axes do not agree with one another in optical efficiency, the disadvantage arises that the distribution of the illuminance becomes non-uniform or the like. This calibration and confirmation requires a lot of time.
(3) In the case in which the printed board is being transported by a carrier robot or the like, a concept is needed for how the substrate can be turned by 90xc2x0 when it is placed on the workpiece carrier. In this arrangement, the carrier device becomes complex and production costs for the entire exposure device also increase.
The invention set forth below was devised to eliminate the aforementioned disadvantages of the prior art. The object of the invention is to construct a device for step-and-repeat exposure of a rectangular substrate in which the irradiation area is shaped to be rectangular by an integrator lens which progressively exposes the respective exposure zones on the rectangular substrate, in which the irradiation area on the substrate can be switched according to the exposure zones on the substrate without replacing the integrator lens and without changing the direction of the substrate which is placed on the workpiece carrier.
This object of the invention is achieved as follows:
In an exposure device which progressively exposes the respective exposure zones with a rectangular shape (the lengthwise and transverse sides being of different length) on a substrate, there is provided an integrator lens in which several lenses, in the lengthwise and transverse direction, are located parallel to one another, with a cross section in the direction perpendicular to the optical axis which has a rectangular shape (the lengthwise and transverse sides being of different length), such that the integrator lens optical axis agrees with the optical axis of the incident light, and this integrator lens is rotatably held at either a first position or a second position, the second position being achieved by turning the integrator lens 90xc2x0 around the optical axis of the incident light from the first position on the integrator lens. Furthermore, the position of the integrator lens is switched according to the arrangement of the exposure zones on the substrate into the first position or the second position and thus the irradiation area on the substrate is switched.
This means that the integrator lens, which is changing the light incident on the mask into rectangular light, is turned by 90xc2x0 and exposed when the shape of the exposure zones is changed from xe2x80x9cmore long than widexe2x80x9d to xe2x80x9cmore wide than longxe2x80x9d or from xe2x80x9cmore wide than longxe2x80x9d to xe2x80x9cmore long than widexe2x80x9d, as shown in FIGS. 4(a) and 4(b).
In this way, the irradiation area on the substrate can be switched by simple activation without replacing the integrator lens or without changing the direction of the substrate which is placed on the workpiece carrier. Thus, exposure can be done according to the arrangement of the exposure zones on the substrate.
Furthermore, adjustment of the optical axis after switching is not necessary due to the fact that the integrator lens is turned by 90xc2x0 around the optical axis. Thus, the device can be greatly simplified and costs reduced.